The overall goal of the proposed project is to define the contribution of joint hypermobility to lower body osteoarthritis (OA). Results of this study wil inform clinical practice and determine groups at high risk for OA who require targeted prevention or intervention approaches. The rationale for the proposed research is that: 1) joint hypermobility changes joint mechanics, 2) joint hypermobility is an expected independent risk factor for OA, and 3) joint hypermobility increases the risk of injury, a major risk factor for OA. The central hypothesis is that joint hypermobility is associated with lower body OA (lumbar spine, hips, knees, ankles, and feet) and that joint hypermobility magnifies the effects of other OA risk factors (i.e., joint injury). In Aim 1, we will assess the cross-sectional and longitudinal relationships of joint hypermobility with prevalent, incident, and progressive lumbar spine, hip, and knee OA. We will examine these relationships by age, sex, and body mass index because joint hypermobility declines with age, is more common in women than men, and varies with obesity. In Aim 2, we will evaluate whether joint hypermobility interacts with joint injury with regard to prevalent, incident, and progressive lumbar spine, hip, and knee OA. In Aim 3, we will explore the cross- sectional relationship of joint hypermobility and prevalent OA at the foot and ankle, joints that have not been examined in prior studies of joint hypermobility and OA. To achieve these aims, we will conduct the largest study to date of over 6900 participants from three large studies of participants with and without OA. OA, injury, and joint hypermobility data were consistently and identically measured across all 3 studies. The multidisciplinary team includes collaborative and productive researchers and clinicians with expertise in OA and injury epidemiology, rheumatology, musculoskeletal radiology, biomechanics, and biostatistics. The Principal Investigator is an Early Stage Investigator, an OA and injury epidemiologist, and an experienced physical therapist. She is in her final year as a NIH/NCATS (National Center for Advancing Translational Sciences) KL2 Scholar in which she is developing independent research on non-pharmacologic / non- surgical interventions for biomechanical risk factors of OA.